Protective garments are now well known for many and varied uses, such as suits for industrial workers, firefighters, wildlands firefighters, race car drivers, airplane pilots, and military personnel. Garments include not only complete, full body suits, but also individual garments such as trousers, jackets, gloves, boots, hats, head coverings, masks, etc. Generally, protective garments are designed to shield a wearer from a variety of environmental hazards. Firefighter garments are representative of such protective garments.
Firefighter garments, generally known as turnout gear, are designed primarily to prevent the firefighter from sustaining serious burns. A second significant threat to firefighters is heat stress. More firefighter deaths occur in the United States each year due to heat stress related conditions than due to burns. Heat stress related conditions include elevated body core temperature leading to heat prostration, increased blood pressure, heatstroke, and sometimes heart attack. As this second threat has become recognized, the fire service community has attempted to modify and improve turnout gear to minimize its contribution to heat stress.
Generally, turnout gear includes a coat and overalls. Turnout gear typically comprises three layers: an outer shell, a moisture barrier, and a thermal barrier. The outer shell layer is usually a woven fabric made from flame resistant fibers and is considered the firefighter's first line of defense. Not only should it resist flame, but it needs to be tough and durable so as not to be torn, unduly abraded, or snagged during normal firefighting activities.
The moisture barrier layer, while also flame resistant, is provided to prevent water from penetrating and saturating the turnout gear. Excess moisture from the environment would laden the firefighter with extra weight and therefore increase their load. Such an increase in load is likely to increase the possibility of heat stress.
The thermal barrier liner is also flame resistant and offers the bulk of the thermal protection afforded by the ensemble. A traditional thermal barrier liner includes an insulation layer of flame resistant fibers quilted to a lightweight woven face cloth also made of flame resistant fibers. A material commonly used as a component in the thermal barrier, and often regarded as an industry standard, is known as E89® from DuPont of Richmond, Va. E89 is a spunlaced nonwoven material consisting of NOMEX® (meta-aramid) staple or KEVLAR® (para-aramid) staple or a combination of both, Technical Guide for NOMEX® Brand Fiber, H-52720 Revised July 2001 by DuPont, Richmond, Va., page 3.
While E89 is an excellent material, there is a need to find better materials, i.e., materials with the same or better thermal protection and lower weights.
Nonwovens used in thermal layers have been suggested and they are disclosed in U.S. Pat. Nos. 4,937,136, 5,136,723, 5,236,769, 6,430,754, 6,743,498, 7,6768,55, and US Publication 2002/0069453.
U.S. Pat. No. 4,937,136 teaches an inner thermal liner made with a nonwoven fabric of a blend of wool and a synthetic fiber capable of high temperature performance. The synthetic fibers include, among others, NOMEX, KEVLAR, and polybenzimidazole (PBI).
U.S. Pat. No. 5,136,723 teaches an inner thermal barrier made with a mesh (apertured) fabric of NOMEX or KEVLAR having a basis weight of about 2 osy (ounces per square yard) or 67.8 gsm (grams per square meter). This mesh fabric is believed to be E89.
U.S. Pat. No. 5,236,769 teaches textile layer of a nonwoven made with 100% aramids, mixtures of 30-50% wool and heat stable fiber, such as PBI. This nonwoven has a basis weight of 200 gsm (5.9 osy) at a thickness of 4 mm.
U.S. Pat. No. 6,430,754 teaches a second layer of insulating material of 1.5 osy E89 or a spunlaced nonwoven of a blend of aramid and PBI fibers. U.S. Pat. No. 6,430,754 also teaches an alternate embodiment where the thermal barrier has a first layer of 2.3 osy E89 (spunlaced nonwoven) and a second layer of 1.5 osy E89 (spunlaced nonwoven).
U.S. Pat. No. 6,743,498 teaches an insulating barrier of a perforated nonwoven having a basis weight in the range of 100-200 gsm and made from a variety of thermostable fiber including, among others, aramids and PBI.
U.S. Pat. No. 7,676,855 teaches an insulation layer of a nonwoven made of, among other things, aramids or melamines (but no PBI), the nonwoven maybe hydroentangled, and the basis weight of the nonwoven may be in the range of 0.75-8 osy. In the exemplary examples, the nonwoven is 2.5 osy and made of 50% BASOFIL® melamine/25% meta-aramid/25% para-aramid.
US Publication 2002/0069453 teaches the insulation layer comprising a blend of inherently hydrophobic fibers and non-hydrophobic, flame resistant fibers. The hydrophobic fibers include polytetrafluoroethylene (PTFE) fibers. The non-hydrophobic fibers include aramid fibers, PBI fibers, polybenzoxazole (PBO) fibers, melamine fibers, and blends thereof.